Desertification$\_\_$

A$.$

leads to the loss of the primary resources$-$fertile topsoil, vegetation, and crops$-$that sustain economic activity.

B$.$

is protected by the United Nations Convention to Combat Desertification with treats the problem regionally, rather than by a country specific approach, recognizing that poor countries may not be able to create their own action plan.

C$.$

is caused only by climactic variations, human activities do not contribute to the process.

D$.$

is unrelated to productivity, a matter solely determined by education and good governance.